1. 7 September 2015 Name the following by using what you have already memorized! 1)Li 3 PO 4 2)NaOH 3)CaSO 4 4) KNO 3 Pick up a BellWork sheet, to start fresh!

2. Bellwork 9/10/15 Name three people that contributed to the history of the atom and list at least two facts about each person.

3. Think about what you think an atom looks like & how to describe its size; write his in your notes.

4. Today we are going to… Explore the size of an atom. Discover the historical development of the atom.

5. Ancient Greeks Aristotle believed that there are only four elements in the universe.

6. 400 B.C.E. Proposed that matter was composed of tiny indivisible particles Based on thought not experimentation Coined the Greek term “Atomos” meaning-- indivisible Democritus

7. 500BCE to 1720 Mixture of science and mysticism. Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists. Alchemists

8. Dalton Noticed that all compounds had something in common. No matter how large or small the sample was.

9. Dalton’s Theory All elements are composed of atoms.

10. Dalton’s Theory All atoms of the same element have the same mass, and atoms of different elements have different masses.

11. Dalton’s Theory Compounds contain atoms of more than one element.

12. Dalton’s Theory In a particular compound, atoms of different elements combine in the same way.

13. Dalton’s Model Dalton's model of the atom, a solid sphere was an early model of the atom.

14. Daltons Atomic Theory All matter is made of atoms A chemical reaction is a rearrangement of atoms Postulate 1 All atoms of an element are identical in mass and property Compounds are formed of two or more types of elements Postulate 2 Postulate 3 Postulate 4 Postulate 5 Atoms are indivisible and indestructible

15. Dalton’s Theory Errors Mostly holds up today with only a few errors. Atoms are made of protons, neutrons, electrons Postulate 2 Atoms are indivisible and indestructible

16. Dalton’s Theory Errors We now know of the existence of isotopes. Atoms of the same element that have different masses Other than that…everything else is correct. All atoms of an element are identical in mass and property Postulate 3

17. Thomson’s Experiment

18. Thomson’s Model

20. Thomson Provided the first evidence that atoms are made of even smaller particles.

21. From his experiment he discovered that there were negatively charged particles in the atom, which he called electrons He designed a model of the atom, called the plum pudding model. This atomic model: a positively charged jelly-like atom with “corpuscles” of negative charges called electrons

22. Rutherford’s Experiment

23. Experiment Animation Gold Foil Experiment

24. Rutherford’s Model All of an atom’s positive charge is concentrated in its nucleus.

25. Rutherford Model Nuclear Model dense, positive nucleus surrounded by negative electrons

26. Bohr Model Niels Bohr (Danish Physicist) Electrons move around the nucleus of the atom the same way that planets move around the sun.

27. Foundation of the Bohr Model  Each electron has a specific amount of energy  If an atom gains or loses energy, the energy of an electron can change.  The possible energies that electrons in an atom can have are called ENERGY LEVELS  An electron in an atom can move from one energy level to another when the atom gains or loses energy

28. Bohr Model  Planetary System Model  Positively Charge Nucleus  Electrons orbiting the nucleus in fixed energy levels  “Excited” electrons jump energy levels